<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .test{
            float: left;
            width: 400px;
        }
    </style>
</head>
<body>
<div>
    <div class="test">1</div>
    <div class="test">2</div>
    <div class="test">3</div>
</div>
<script>
      function  test(){
           this.a={
               b:function (){
                   console.log(this)
               }
           }
      }
      var am =  new test();
      am.a.b();
</script>
</body>
</html>